1. Field of the Invention
This invention relates to a target for use in a photogrammetric analytical measurement system, in which a survey map is produced on the basis of a set of photographed pictures obtained at two different photographing positions.
2. Description of the Related Art
For example, photogrammetry is carried out at a traffic accident spot. The traffic accident spot is photographed by a camera in at least two different positions, and a survey map of the traffic accident spot is produced based on a set of photographed pictures obtained at the different positions.
In particular, a two-dimensional coordinate system is defined on each of the photographed pictures, and two-dimensional positions of the objects, which are recorded on each picture, are determined by the two-dimensional coordinate system. Then, a three-dimensional coordinate system is defined on the basis of the two sets of two-dimensional coordinate systems, and three-dimensional positions of the recorded objects are determined from the three-dimensional coordinate system. Accordingly, it is possible to produce a survey map of the traffic accident spot by drawing the objects on a sheet of paper in such a manner that the objects are projected on one of the three planes defined by the three-dimensional system.
Before accurately scaled distances and lengths can be reproduced on the survey map, a standard measurement scale must be recorded together with the objects in the photographed pictures. Also, a standard reference plane, on which the survey map should be drawn, must be defined in the photographed pictures.
Usually, in order to define the standard measurement scale and the reference plane, three respective cone-shaped markers, which are identical to each other, are positioned at suitable locations around a traffic accident spot. Namely, a distance between two apexes of the cone-shaped markers is measured, for example, with a measuring tape, and set as the standard measurement scale, and a plane, defined by the three apexes of the cone-shaped markers, is utilized as the reference plane. As the positioning of the cone-shaped markers and the measurement of the distance between the two apexes are performed by operators, a process of preparing for photographing is onerous and requires a lot of time.
In order to solve the above mentioned problems, photogrammetric analytic measurement, using a target which has a triangular frame instead of the three cone-shaped markers, is disclosed in Japanese Unexamined Patent Publication (Kokai) No. P10-170263. Standard point members are respectively mounted on each of three apexes of the target. A distance between the standard point members is set as the standard measurement scale, and a plane defined by the standard point members is utilized as the reference plane. A reflecting sheet, for example, is attached on the standard point members so that the standard point umbers can be viewed easily in photographed pictures.
However, if photogrammtric analytic measurement is performed under condition in which an amount of luminance is not ideal for photographing, for example, in rain or at nighttime, or at a spot, in which a surface of a road reflects incident light, the standard point members can not be viewed clearly in photographed pictures. Accordingly, the standard measurement scale and the reference plane are not accurately determined, and thus the photogrammetric analytic measurement can not be performed accurately.
The determination of the three-dimensional positions of the recorded objects from the three-dimensional coordinate system is carried out by iterating a series of approximate calculations, using a computer having a monitor on which the set of photographed pictures is displayed.
Initially, before a first series of approximate calculations is executed, the apexes of the cone-shaped markers and a suitable point on one of the recorded objects in the set of photographed pictures displayed on the monitor are selected with a cursor, by manipulating a mouse, whereby three sets of two-dimensional coordinates, corresponding to the apexes of the cone-shaped markers, and a set of two-dimensional coordinates on the suitable point of the selected object are inputted to the computer. Namely, the execution of the first series of approximate calculations is based upon the inputted two-dimensional coordinates of the apexes of the cone-shaped markers and the inputted two-dimensional coordinates of the suitable point on the selected object, thereby determining three-dimensional positions of the apexes of the cone-shaped markers and a three-dimensional position of the suitable point of the selected object from the three-dimensional coordinate to system.
Then, another suitable point on the selected object in the set of photographed pictures displayed on the monitor is indicated with the cursor, by manipulating the mouse, whereby a set of two-dimensional coordinates of the other suitable point on the selected object is inputted to the computer, and a second series of approximate calculations is executed on the basis of the inputted two-dimensional coordinates of the other suitable point on the selected object, thereby determining a three-dimensional position of the other suitable point on the selected object from the three-dimensional coordinate system. This procedure is continued until a sufficient number of points on the selected object are indicated, to thereby specify a three-dimensional profile of the selected object.
The aforementioned series of approximate calculations is executed based on positional data of the camera at which the pictures are photographed. The positional data of the camera includes a distance from the camera to the selected object, an angle of the camera against the object. Accordingly, at the traffic accident spot, it is necessary for an operator to measure and record such positional data.
However, it is onerous to measure the positional data of the camera every time a picture is photographed. Further, the measurement of the positional data of the camera requires a great deal of time and labor. On the other hand, the photogrammetry at the traffic accident is required to be rapidly performed. Accordingly, it is difficult to obtain an accurate positional data of the camera at a photogrammetry spot, such as the traffic accident spot.
Further, before the three-dimensional profile of the selected object can be properly specified and produced, each of the suitable points on the selected object must be precisely indicated with the cursor, by an operator""s manipulation of the mouse. Nevertheless, the indication of the suitable points on the selected object with the cursor, by the operator""s manipulation of the mouse, cannot always be carried out in a precise manner. Of course, unless the precise indication of the suitable points on the selected object can be ensured, the selected object cannot be accurately drawn on the survey map Namely, sufficient work efficiency and accuracy of the photogrammetry can not be obtained.
Therefore, an object of the present invention is to provide a target for photogrammetry, by which positional data of a camera is calculated based on a photographed picture by photographing an object therewith.
In accordance with an aspect of the present invention, there is provided a target for photogrammetric analytic measurement, which is photographed with an object by a camera in the photogrammetric analytic measurement, the target having standard points that are clearly discerned in a photographed picture, and a calculation of photographing positions of the camera being performed by determining a positional relationship of each of the standard points in the photographed pictures, the target comprising: a first standard point member defining a first standard point included in the standard points; a second standard point member defining a second standard point included in the standard points; a third standard point member defining a third standard point included in the standard points; and assistant point members respectively defining assistant points that are clearly discerned in the photographed picture.
Preferably, distances between each of the first standard point and the second standard point and the third standard point, are predetermined. A first straight line connecting the first standard point and the second standard point, and a second straight line connecting the second standard point and the third standard point are inclined at a predetermined angle. At least one of the assistant points are positioned on the first straight line and the second straight line.
Preferably, a distance between the first standard point and the second standard point equals a distance between the second standard point and the third standard point. The predetermined angle is right angle.
Preferably, the first standard point, the second standard point and at least one of the assistant points being positioned on the first straight line, are positioned at equal spaces on the first straight line, and the second standard point, the third point and at least one of the assistant points being positioned on the second straight line, are positioned at equal spaces on the second straight line.
Preferably, a number of the assistant points on the first straight line is different from a number of the assistant points on the second straight line.
Optionally, the number of the assistant points on the first straight line is two, and the number of the assistant points on the second straight line is one.
In accordance with another aspect of the present invention, there is provided a target for photogrammetric analytic measurement, which is photographed with an object by a camera in the photogrammetric analytic measurement, the target comprising: a first bar and a second bar that are connected to each other; at least three standard point members, lying on one plane, that are fixed on the first bar and the second bar; and non-reflecting embers that are respectively attachable to and removable from said at least three standard points.
Preferably, the at least three standard point members respectively comprise a circular portion, a diameter of which substantially equals the width of the first bar and the second bar.
Preferably, each of the non-reflecting members is a circular plate, and a circular opening, a diameter of which substantially equals the diameter of the circular portion of the at least three standard point members, is formed at a center portion of the circular plate.
Preferably, a reflecting sheet, by which a reflecting amount of incident light thereon is increased, is attached on a surface of the circular portion, and a non-reflecting sheet, by which a reflecting amount of incident light thereon is reduced, is attached on a surface of the non-reflecting members. The surface of the circular portion and the surface of the non-reflecting members are on a side opposite to a side of the first bar and the second bar, when the non-reflecting members are respectively attached to the standard point members.
Preferably, the reflecting sheet and the non-reflecting sheet are placed on the one plane.
Preferably, one of each of the at least three standard point members and each of the non-reflecting members comprises a ferromagnet, and another of each of the at least three standard point members and each of the non-reflecting ambers comprises a magnetic material.
Preferably, each of the at least three standard point members comprises a magnet that is ring shaped, a center point of which is coincident with a center point of the circular portion, and each of the non-reflecting members comprises a metal material that is attached to the magnet by magnetic force. The metal material is placed around the circular opening, on a surface opposite to the surface to which the non-reflecting sheet is attached.
Preferably, a reference plane is determined by the standard point members, and the target further comprises: a first tilt sensor that senses a first tilt angle to a horizontal plane around a first axis on the reference plane; a second tilt sensor that senses a second tilt angle to the horizontal plane around a second axis which is perpendicular to the first axis, on the reference plane; an azimuth sensor that senses an azimuth; and a transmitting device that transmits data of the first tilt angle, the second tilt angle and the azimuth by wireless.
Preferably, the non-reflecting members are made of a material through which an electric wave can transmit.
Preferably, the azimuth sensor is placed intermediately between two of the at least three standard point members, which are adjoining.
Preferably, the first bar and the second bar are connected in such a manner that one and of the first bar and one end of the second bar are rotatably connected; when the target is in an operational position, the first bar and the second bar are fixed in such a manner that the first bar and the second bar are perpendicular to each other; and when the target is not in the operational position, the first bar and the second bar are fixed in such a manner that the first bar and the second bar are substantially parallel to each other.
Preferably, the target further comprises: a fixing member that fixes a relational position between the first bar and the second bar in such a manner that the first bar and the second bar are perpendicular to each other, when the target is in the operational position; a hinge that rotatably connects the fixing member to the first bar; a lock hinge by which the fixing member is attachable to and removable from the second bar.
Preferably, the target further comprises: a first fixing mechanism that fixes the second bar to the first bar such that the second bar is parallel to the first bar when the target is not in the operational position; a second fixing mechanism that fixes the fixing member to the first bar such that the fixing member is placed between the first bar and the second bar when the target is not in the operational position.